Carboxyl group-containing polymers such as sodium poly(meth)acrylate are widely used in applications of detergent builders, pigment dispersants (dispersants for inorganic particles), and water treatment agents (anti-deposition agents for preventing deposition of a scale component), for example. These markets have demanded the polymer having higher performance.
Methods for filling such needs include a method of producing a polymer disclosed in Patent Literature 1 in which a chain transfer agent is continuously added for a predetermined period during polymerization wherein an addition rate of the chain transfer agent is changed at least once. In the disclosure, this method can reduce the amount of the remaining monomer to improve the safety of the polymer to be obtained. Moreover, the concentration of the monomer in the reaction solution can be further increased to improve the productivity of the polymer and produce the polymer at low cost. Further, the polymer to be obtained can have narrower molecular weight distribution, and demonstrate high performance (such as dispersion performance) when the polymer is used as a detergent builder or an inorganic pigment dispersant, for example. Patent Literature 1 also discloses use of sodium hypophosphite as the chain transfer agent.
Moreover, for example, Patent Literature 2 discloses a calcium carbonate aqueous suspension containing at least one co-grinding agent comprising at least one homopolymer and/or at least one copolymer of a partially neutralized acrylic acid whose molar neutralization rate of acid functional groups is less than 75% of the total acid functional groups.
Moreover, for example, Patent Literature 3 discloses a process of polymerizing or copolymerizing acrylate monomers to form low molecular weight water-soluble acrylate polymers using a hypophosphorous acid chain transfer agent together with polymerization initiators, water and optional polymerization activators in a heated, agitated aqueous polymerizing mixture containing the monomers, the process comprising concurrently feeding hypophosphorous acid chain transfer agent and an alkaline neutralizer to the polymerizing mixture of monomers such that the alkaline neutralizer is present during at least most, if not all, of the polymerization in an amount sufficient to neutralize at least 20% of the acid groups of the carboxylic monomers present. In the disclosure, according to the polymerization process, a low molecular water soluble polycarboxylate polymer composition with high levels of dialkyl phosphinate polymers and low levels of unreacted or unincorporated hypophosphite or phosphite inorganic compounds where greater than 50% of the phosphorus present is in the dialkyl species and less than 20% is in inorganic phosphorus containing acids or salts is obtained. Moreover, Patent Literature 3 discloses a composition having a large content of a dialkyl polymer and a low content of an inorganic compound which is useful in end-use applications such as dispersants for paint blended products, additives for washing detergents and detergents for dish washers, dispersants for kaolin clay slurries and anti-scale agents, dispersants for water treatments and oil production, and corrosion inhibitors.
Moreover, for example, Patent Literature 4 discloses a detergent builder containing a poly(meth)acrylic acid (salt) polymer as an essential component wherein a product of an anti-gelation ability (A) and a chelating ability (B) (A×B) is not less than 18,000. Patent Literature 4 discloses a detergent builder obtained using a polymer having narrower molecular weight distribution, a high anti-gelation ability, and a high chelating ability.